This invention relates to a mechanical actuating mechanism and particularly to an electrically driven system for adjusting the swashplate angle of a parallel type Stirling cycle engine.
In one type of Stirling cycle engine, a swashplate is journaled for rotation within the engine housing. The swashplate is driven by crossheads (or vice versa) which are connected to reciprocating pistons. The swashplate, in turn, is coupled to a drive shaft for mechanical power transfer. As a means of varying the input or output of the machine, a variable swashplate angle mechanism can be employed which varies the stroke of the pistons.
Stirling Thermal Motors, Inc., assignee of the present invention has previously designed and implemented actuator systems for a variable angle swashplate which uses a hydraulic motor to control swashplate angle. Although such actuators operate satisfactorily, they require intricate fluid control systems for accurate adjustment of swashplate position. Another disadvantage of hydraulically driven actuators is the requirement that a precisely controlled hydraulic pressure must be applied continuously during operation of the device. There is accordingly a need in the art to provide an improved variable angle swashplate actuating mechanism which avoids the above mentioned shortcomings of present designs.
In accordance with the present invention, a number of embodiments of electrically driven swashplate actuation systems are described. For each embodiment, a different transmission is used to communicate rotation of an electric drive motor to the swashplate unit. Die to the high reduction gearing used to drive the swashplate, sufficient friction is present to prevent back driving of the gear train, thus avoiding a requirement for continuous energization of the actuator motor.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.